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Date: Tue, 1 Jan 2013 15:46:30 -0800
Message-ID: <CAJ-Vmok_UDVykup4xHCigrBbzErOhUQOZMATJ+=qkBFOHQS+Bg@mail.gmail.com> (sfid-20130102_004635_878429_676C188D)
Subject: Re: [PATCH] nl80211: allow ad-hoc to set WMM parameters from outside
From: Adrian Chadd <adrian@freebsd.org>
To: Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>
Cc: Johannes Berg <johannes@sipsolutions.net>,
	linux-wireless@vger.kernel.org, linville@tuxdriver.com,
	mathias.kretschmer@fokus.fraunhofer.de,
	Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
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Sender: linux-wireless-owner@vger.kernel.org

I've been looking at WME parameter handling for FreeBSD's net80211
stack (with and without 802.11n support.)

Yes, the problem is figuring out what the actual BSS configuration
_should_ be. You could potentially hear a variety of different WMM
parameters from a variety of different nodes in the BSS (depending
upon how buggy their WMM IE handling in adhoc mode is, I guess) so you
can't just simply update the WMM parameters based on what you hear
from peers.

What I have thus far:

* When creating a BSS, used the stored values;
* When joining a BSS, use the configuration from the BSS node you've
initially decided to "join" against, and hope they're actually
"correct";
* When doing a BSS merge, use the configuration from the BSS node that
you're joining to;
* If a different BSS configuration is heard from the node you joined
against, update your local configuration;
* .. and set a timer that enforces you don't change your configuration
for another 'n' ms (for n > 1000?) even if the joined/merged BSS ID
changes its config.

STA mode operation has the STA listening to changes in the BSS. It
only hears these frames from the active AP so you don't have churn if
you hear different WMM IEs from different APs (in the same SSID.)
adhoc is slightly crazier there.

My only concern is having oscillating BSS updates propagate across the
network in a rather silly looking fashion. Hence the BGP 'route
dampening' style timer to try and ensure that doesn't occur.

It'd be nice if we could come up with a unified way of doing this and
have it interoperate between FreeBSD/Linux (and any other vendor
adhoc+wmm implementations out there.)

Thanks,


Adrian